Problems exist in scaling low power RF-excited gas discharge lasers up to higher powers. The RF power distribution tends to become uneven over the discharge area and can concentrate in one spot, thereby disrupting what would otherwise have been a uniformly excited discharge suitable for efficient laser power extraction. Increasing power is achieved by increasing the gas gain volume that further requires increasing the volume of the laser discharge region. Because increasing discharge length also increases the discharge volume, and because low power RF-excited gas discharge lasers do not typically change in cross-section significantly, it is therefore convenient to speak of power scaling in terms of length scaling. Every one (1) cm increase in laser discharge length will result in an increase of laser output power of approximately 0.5 Watts. Some disadvantages of length scaling are a corresponding increase in the size of the laser, and an increase in the frequency of discharge instabilities and further risk of exceeding the intensity damage threshold of the laser mirrors.
Additionally many RF excited lasers form a sheath on the surface of the electrodes, both on the positive and ground electrodes. The sheath has a thickness that is significant enough to disturb or perturb the mode of the laser in the axis of the sheath. The mode disturbance or perturbation can result in oval beam outputs that are undesirable when trying to focus with a circular lens.